Since its inception in 1999 over 20 nations have committed support
towards building the Argo array, and a number of other countries
have assisted in deploying floats. Deployment of Argo floats
started in 2000 and expectations are that the array should approach
the 3,000 float target by 2007. The present status of the array
is shown in the figure below (produced by JCOMMOPS Argo Information
Centre).

Traditionally, temperature and salinity profiles have
been provided by bathythermograph soundings from naval
and merchant vessels, and sampling from research vessels.
The bulk of the data is from merchant vessels taking
part in the Ship
of Opportunity Programme (SOOP), and is mainly confined
to shipping lanes.

The expectation of Argo is to have approximately 3,000
profiling floats (giving a spacing of about 3° or
300 km) deployed globally. The figure (taken from the
Argo brochure) illustrates the projected
coverage of floats once Argo is fully established,
illustrating the significant improvement in data coverage
over that which is currently available. In particular,
through air dropping, floats can be deployed in the remotest
regions of the ocean.

Argo floats drift at a parking depth of typically 1,000
m, descending to 2,000 m and then rising to the surface
every 10 days to record a temperature
and salinity profile and transmit these data back
via satellite (currently using System ARGOS) before
returning to their parking depth and continuing another
cycle.

A schematic of the mission
cycle is shown in the figure (taken from the
Argo Brochure). Argo floats are expected to be capable
of making as many as 150 cycles, and operate for
four years. Each Argo float (including its antenna)
is typically 2 to 2¼ m long and up to 30 kg
in weight. Currently there are two commercial float
manufacturers: Webb
Research Corporation and Martec.